MTC9000 ticking

[big10p]

It's been a while, so just need to check. Chassis is ticking with B+ dancing around the 80v mark. The HOT tests ok out of circuit. Is this definitely a bad lopt, then? Bit annoying if it is, as it's a recent replacement. ☹️

Thanks.

 

[big10p]

Ok, I isolated pins 1 and 3 on the flyback and connected a bulb to the B+, which is now a steady 127v, so it looks like the lopt has gone. Again. ☹️

 

[stevebm1]

Bummer,was it the one from tecknoservice in spain?,I know someone else who had a faulty one from their batch they were selling

 

[big10p]

Bummer,was it the one from tecknoservice in spain?,I know someone else who had a faulty one from their batch they were selling

Pretty sure it is, yeah. It has been working ok for a while. I bought a spare at the same time so will see how long this one lasts...

 

[tb2000]

What version of MTC9000 is it? Some used the HR7107 and some used the HR7025. To be honest, from personal experience either lopt should work in either chassis but if you've had trouble with HR7025 use a HR7107 or vice-versa. Oh and check your poly caps. I've not seen a bad poly cap bust a lopt before (not an obvious cause anyway) but you never know if you've got one putting strain on the lopt.

 

[big10p]

What version of MTC9000 is it? Some used the HR7107 and some used the HR7025. To be honest, from personal experience either lopt should work in either chassis but if you've had trouble with HR7025 use a HR7107 or vice-versa. Oh and check your poly caps. I've not seen a bad poly cap bust a lopt before (not an obvious cause anyway) but you never know if you've got one putting strain on the lopt.

It's a BZ 02.

With this lopt.

Does this look ok? I've replaced the poly caps in the past (as in pic). Should I still pull and test them? Thanks.

 

[tb2000]

Yeah, looks ok. That's an equivalent of the HR7107 so should be fine, and is correct for that revision according to the schematics. As you've done the HV poly caps already I wouldn't expect them to be bad already. You could try the HR7025 but it probably wouldn't be any different.

 

[big10p]

Hmm. I've replaced the flyback with an identical one from tecknoservice. Power up and I'm getting nothing. No electrical sound, static buildup or neck glow. B+ measures at a solid 157, but maybe this is high because there's no load on it for some reason?

Any ideas what to check? Thanks.

 

[big10p]

Hold up, I think I've found the issue. A very well hidden broken trace under a repair (this chassis is in a bit of a state, but I'm not giving up on it yet). The trace goes to pin 1 of the flyback...

 

[big10p]

Yep, that was it. Weirdly, the trace looked ok to the naked eye, once I'd removed the solder from the repair. Must have been a micro fracture across it, as there was no continuity between two joints connected by the trace. Anyway, working now, but will have to see how long this lopt lasts...

P.S. not a Robotron cab, just a JAMMA cab themed to it. 🙂

 

[gunblade]

well done, chassis fractures are very difficult to find